Fig. 3

YFP expression levels mirror the endogenous dynamics of PAX7. a–h Regeneration of the TA muscle was induced by injection of cardiotoxin (CTX). H&E staining of cross-sections of TA muscle in Pax7^+/+ and Pax7^YFP/+ mice, 0, 3, 7, and 14 days following CTX injection, scale bar 50 μm (a). Q-PCR analysis of gene expression dynamics of myogenic regulatory factors (Pax7, Myf5, MyoD, and Myogenin) and YFP during muscle regeneration (b–f). Data represent means ± s.e.m. (ND, not detected; n = 3–5, per group). g Immunohistochemistry for YFP and Laminin α2 proteins in cross-sections of TA muscle isolated from Pax7^+/+ or Pax7^YFP/+ mice at day 3 after CTX injection, scale bar 50 μm. h Immunohistochemistry for YFP and PAX7 proteins in cross-sections of TA muscle isolated from Pax7^YFP/+ mice at day 3 after CTX injection, scale bar 10 μm. i–o Satellite cells were isolated from limb muscles of Pax7^YFP/+ mice and cultured in growth medium (GM). Myogenic differentiation was induced by differentiation medium (DM) for 3 days. Representative images are shown (i), scale bar 100 μm. j–o Q-PCR analysis shows a positive correlation between Pax7 and YFP mRNA levels during myogenic differentiation [quantified in (o) (R² = 0.8663; n = 12)]. Data represent the mean ± s.d. (n = 3, each group). p Co-immunostaining revealed a positive correlation between YFP and PAX7 protein levels in satellite cells maintained under GM conditions. Fluorescence intensity was measured using the CellInsight CX5 Platform